Soundproofing - talk me off the ledge here

[Rodolfo Lasparri]

I'm now pressed to soundproof/vibration dampen the interior of my '73 tii. It was stripped to bare metal by yours truly and POR 15 treated, primed, painted. I am hesitant to seal it up with Dynamat or the like and wanted some insight here. The collective wisdom of the group as to whether I should second skin, dynamat (or similar - sigh, but I have some), MLV, other, etc. would be appreciated.

 

For added reference - I really don't like the idea of placing a butyl product on top of clean paint after stripping all the tar. I'd prefer to see/know if anything was amiss in the future so my thought is a second skin or similar as a first option and I really don't like the weight aspect of a Dynamat/MLV either.  Inner doors, floor, and rear seating area are of primary concern. So please don't hold back - hit me with it!

[Mike Self]

I've been using ordinary household carpet padding under my car carpets (and under the rear seat cushion, and hung behind the rear seat back) for many years.  Great for sound deadening, and very inexpensive--often free as you can usually scrounge some good-sized scraps from your local carpet emporium.  

 

I used to use "waffle padding" because if it got wet, the waffle pattern would allow air circulation and it would dry quickly.  But you can't find it any more, so I use padding that is treated to be waterproof--actually pet pee-proof--just as good.  All you have to do is cut it to fit and put it in place.  The carpet will hold it down so you don't need to glue it.  Half inch or 5/8 inch padding is more than enough.

 

Just don't use it inside your doors--way too wet in there.  

 

mike

[AceAndrew]

44 minutes ago, Rodolfo Lasparri said:

So please don't hold back - hit me with it!

 

Rodolfo, you've over thought this to the point of being indecisive.  You are going to second guess nearly every comment, as you should, because our experiences will vary.

 

Cracks or chips in any coating will allow for water ingress.  Much of any abatement will be due to your own due diligence and attentiveness.

 

I like butyl plus thin layer of carpet padding in footwell areas, but again... to each their own.  

[M3M3]

and as has been covered before in other threads,  dynamat/rammat type products are not used to cover everything in a "second skin".  you only use a limited amount to kill the vibrations of the panel.  a second layer of a sound absorbing foam type material is then used to cover everything.   

[NYNick]

Check it out. I took 19 lbs of sound proofing off the floor of my car, and added 6 lbs of MLV and Cold KOOL insulation. Nothing is glued except on the tunnel and rear seat back. I want to be able to get under everything if need be at some point down the road.

[TobyB]

If the mass isn't solidly adhered to the metal, it doesn't dampen transmissive noise.

 

Me, I go without even carpets, and wear earplugs.

 

t

lightness=horsepower

[AceAndrew]

16 minutes ago, TobyB said:

If the mass isn't solidly adhered to the metal, it doesn't dampen transmissive noise.

 

Me, I go without even carpets, and wear earplugs.

 

t

lightness=horsepower

 

It was at this moment I realized @danco_'s character arc will end with him simply turning into @TobyB

[danco_]

8 minutes ago, AceAndrew said:

 

It was at this moment I realized @danco_'s character arc will end with him simply turning into @TobyB

[JerryC]

The original stuff got through 50 years already. Are you worried about the next 50 years? For me, the best weight reduction for driving would be for me to lose about 25 pounds off the driver's seat. Just sayin'...

 

I would be inclined to use the stuff I already have. Maybe just replace the old tar stuff where it was and leave the rest. You'll never make it as quiet as a 2023 BMW, it's a 50 year old car. If you feel like you didn't do enough, add some more later when you go "under the carpet" for the inspection you mentioned.

-Jerry

[tech71]

Whatever you use.. dont make it too thick. Makes your carpet look "puffy"

[BarneyT]

I have used dynaPad which comes in a roll 30”x60” or something like that it is different from dyanmat, the dynaPad works great on tunnel/firewall for sound I contact cement it on…240 in driver seat not worried about the weight.

Edited February 7, 2023 by BarneyT

[Rodolfo Lasparri]

Thank you all - some great stuff here from everyone and I appreciate all the input. I think the consensus that makes sense to me is a blend of dampening some locations and padding some others. I like access @NYNick still has so I will definitely incorporate that and padding. Those along with some dampening as suggested by @AceAndrew and @BarneyT. Really appreciate all the feedback.

 

[TobyB]

8 hours ago, AceAndrew said:

 

It was at this moment I realized @danco_'s character arc will end with him simply turning into @TobyB

I somehow feel both guilty and slightly dirty, now...

 

t

 

[0257]

There’s not enough weight in dampeners and closed-cell foam to matter (at least in a tii) unless you’re tracking your car or your compression is too low.  The real weight (and sound deadening) comes when you install mass loaded vinyl mats on top of the dampener.  Those are heavy.  I generously used Secondskin dampener and on all surfaces except floors I used closed-cell foam — works great on the tunnel, for instance, but don’t go too thick. Between those two products the car got less tinny.  But the SecondSkin mass loaded vinyl on the floors and back deck are what bring down the decibels.  Laid directly over the dampener, no glue.  I think it was worth it.

 

As for being able to see damage underneath the dampener, I get that.  But I concluded that, as tight as that stuff sits on the surface (properly applied), moisture penetration is actually unlikely.  Of course, I bombproofed the heater box aperture, which I hope you’re doing as well.  Plus, even if there’s some risk of rust developing in time, between the bombproofing, the POR-15 and the sticky stuff, the damn thing is likely at least to outlast me, at least.🤷‍♂️

 

Having said all that, to be able to hear The Water Song worth a damn at 65 mph with the windows up, I still have to turn it up to 11.

 

 

[M3M3]

LOL..the real weight of all this sound deading  effort is in all the amps , speakers and subboxes folks put in trying to make a concert hall out of a 70's tin box!  🤣

 

after my early efforts to make my 02 quieter, i ended up just replacing the stereo system with an S14. 

Edited February 8, 2023 by M3M3M3